You can always use the standard retina resolution to get bigger text and icons, I misunderstood and thought people were trying to get more resolution on the Windows side. The standard retina display setting on the 13" machine results in a virtual 1280x800 display (four real pixels per virtual pixel). The Windows side will also run at 1280x800 when you've made that selection, as long as you make sure the "Use full resolution for Retina display" is NOT checked. Both sides will run at the same resolution.
I'm running Win8 in a Fusion VM and my display looks great. I don't see any problems or significant differences between the Mac side and the Windows side. No jaggies or pixelation. Everything is clear and very readable. Maybe it's a difference between Win8 and Win7? But that doesn't make sense to me...
Are you guys running your Windows apps in Unity mode? Maybe that's the issue? I'm running in single-window or full-screen, Unity gets too confusing for me.
Another thing to check is the state of "ClearType" on the Windows side. I've got it turned on, maybe it's turned off in your Win VMs? Easiest way to find it is to open the Windows Control Panel and type "clear" in the Control Panel's search box (upper right of the Control Panel). From there you can start the ClearType wizard to enable it.